1. Field of the Invention
The present invention relates to a thin-plate supporting container for supporting and housing therein a plurality of thin plates such as semiconductor wafers. More specifically, the invention relates to a thin-plate supporting container which can adjust the internal pressure in accordance with the pressure and temperature changes in its surroundings when a plurality of thin plates such as semiconductor wafers are stored and conveyed in the container.
2. Description of the Prior Art
Various types of measures have been taken against problems caused in a case where a thin-plate supporting container is conveyed or transported when the surrounding pressure and temperature change. For example, in the case of transportation by aircraft, the air pressure in a cargo compartment is greatly decreased in a high flight. For that reason, when the thin-plate supporting container is maintained in an airtight state, the internal pressure is remarkably higher than the outside air pressure. As a result, there is a problem in that the container expands or the air in the container leaks out, so that it is not possible to open the lid thereof after the aircraft is landed. In addition, when the surrounding temperature is increased during transportation, there is the same problem.
As one of measure directed such problems, a semiconductor-wafer supporting container is proposed in Japanese Utility Model Publication No. 2-49721.
As shown in FIGS. 11 and 12, this semiconductor-wafer supporting container 1 generally comprises a container body 3 for supporting and housing therein a plurality of semiconductor wafers 2, a lid 4 for covering the upper side of the container body 3 to maintain the interior of the container body at an airtight state, and a molecule filter 5 integral with a side wall 3A of the container body 3 for allowing air to enter and exit the container body 3.
By providing this molecule filter 5, air can enter and exit the semiconductor-wafer supporting container 1 through the filter 5. As a result, even if the pressure change is caused between the inside and outside of the container 1 due to the change in the outside air pressure and so forth, it is possible to maintain the internal pressure at the same value as that of the outside air pressure, so that it is possible to prevent the problems such as the expansion of the semiconductor-wafer supporting container 1.
However, in the case of the molecule filter 5, since the air passing rate is extremely slow, it is not possible to respond to the rate of the pressure change caused in the cargo compartment of aircraft and so forth. In order to allow a quick response, the area of the molecule filter 5 must be increased. However, when the molecule filter 5 is mounted on the container body 3, the area thereof is restricted. Therefore, the semiconductor-wafer supporting container 1 having the molecule filter 5 has not been put to practical use.
In addition, the whole semiconductor-wafer supporting container 1 must be washed before the semiconductor wafers 2 are housed therein. In this case, if the semiconductor-wafer supporting container 1, on which the molecule filter 5 is mounted, is washed, foreign matters such as dust are adhered to the molecule filter 5. If the semiconductor-wafer supporting container having the molecule filter 5, to which the dust or the like is attached, is used, the impurities adhered to the molecule filter 5 are scattered in the container 1. Therefore, such a container can not suitably be used. For that reason, the semiconductor-wafer supporting container 1 must be washed before the molecule filter 5 is mounted thereon.
In addition, since a great amount of dust or the like is adhered to the semiconductor-wafer supporting container 1 after it is used for the transportation of the semiconductor wafers 2, the container 1 must be washed when it is reused. However, if the molecule filter 5 is washed, it can not be used as mentioned above. On the other hand, since the molecule filter 5 is integral with the container body 3, it can not be removed from the container body 3. As a result, the semiconductor-wafer supporting container 1 can not be reused.
Moreover, in a case where the spent semiconductor-wafer supporting container 1 is discarded or recycled, it is required to divide the container 1 into members of different materials. In this case, even if the container body 3 and the lid 4 are made of different materials, they can be easily separated from another to carry out the subsequent processing. However, since the molecule filter 5 is integrally mounted on the container body 3, they can not easily be separated from another. For that reason, there is a problem in that it is difficult to carry out the subsequent disposal and recycling.